Ion implantation is a standard technique for introducing conductivity-altering impurities into a workpiece. A desired impurity material is ionized in an ion source, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the workpiece. The energetic ions in the beam penetrate into the bulk of the workpiece material and are embedded into the crystalline lattice of the workpiece material to form a region of desired conductivity.
Ion implantation has been demonstrated as a viable method to dope solar cells. Two concerns of the solar cell manufacturing industry are manufacturing throughput and cell efficiency. Cell efficiency measures the amount of solar energy that is converted into electricity. Higher cell efficiencies may be needed to stay competitive in the solar cell manufacturing industry. However, manufacturing throughput cannot be sacrificed in order to increase cell efficiency.
Use of ion implantation removes process steps needed for existing solar cell technology, such as diffusion furnaces. For example, a laser edge isolation step may be removed if ion implantation is used instead of furnace diffusion because ion implantation will only dope the desired surface. Ion implantation also offers the ability to perform a blanket implant of an entire surface of a solar cell or a selective (or patterned) implant of only part of the solar cell. Selective implantation at high throughputs using ion implantation avoids the costly and time-consuming lithography or patterning steps used for furnace diffusion. Selective implantation also enables new solar cell designs. Furthermore, ion implantation has been used make solar cells with higher cell efficiencies.
Therefore, any improvement to manufacturing throughput of an ion implanter or its reliability would be beneficial to solar cell manufacturers worldwide. This may accelerate the adoption of solar cells as an alternative energy source.